Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$137.27	10.588%	$151.8041	$151.80	$151.80	$151.80
Purchase #2	$214.60	12.531%	$241.4915	$241.49	$241.50	$241.50
Purchase #3	$107.69	7.807%	$116.0974	$116.10	$116.10	$116.10
Purchase #4	$139.48	6.628%	$148.7247	$148.72	$148.70	$148.70
Purchase #5	$143.47	10.648%	$158.7467	$158.75	$158.75	$158.70
Purchase #6	$204.31	12.213%	$229.2624	$229.26	$229.25	$229.30
Purchase #7	$48.59	12.742%	$54.7813	$54.78	$54.80	$54.80
7 purchase totals =	$995.41		$1,100.9081	$1,100.90	$1,100.90	$1,100.90